The act of upgrading a misdemeanor charge to a felony. This is usually because there are prior convictions for the same crime. In a drug case, it could be because the drug quantity ended up being greater than originally thought, and a felony amount.

Damn, I got caught with a bag of weed. The cops of the scene thought it was a misdemeanor amount. When the lab weighed it, it came back heavy and they felonized me!

I caught a DUI, and because I have three priors, they felonized this one.